Mi amiga lee novelas desde niña y ahora trabaja en una editorial.

Because amiga is the feminine form of amigo. The sentence is talking about a female friend, so Spanish uses mi amiga = my friend (female).

A useful point: mi does not change for masculine or feminine nouns, so you get:

• mi amigo = my male friend
• mi amiga = my female friend

Lee is the third-person singular present tense of leer (to read).

So:

• yo leo = I read / I am reading
• tú lees = you read
• él/ella lee = he/she reads

Here, lee matches mi amiga, which is a third-person singular subject: my friend reads.

It is pronounced as two vowel sounds together: leh-eh.

This is because it comes from leer, where the two e vowels are both pronounced. It is not like a single English lee sound. In careful pronunciation, you hear both vowels.

This is a very common difference between Spanish and English.

In Spanish, when an action started in the past and still continues now, Spanish often uses:

• present tense
  • desde / desde hace

So:

• Lee novelas desde niña
  literally: She reads novels since childhood natural English: She has read / has been reading novels since she was a child

Spanish does not need a present perfect here the way English usually does.

Desde niña means since she was a child or since childhood.

Literally, it is something like from [being] a girl/child. Spanish often leaves out words that English would include.

So:

• desde niña = since she was a little girl / since childhood
• desde pequeño = since he was little
• desde joven = since he/she was young

In this sentence, it tells you that her reading of novels began in childhood and continues up to the present.

Because niña here is being used in a more general descriptive way, not to mean the girl or a girl as a separate person.

Desde niña is a fixed, natural Spanish pattern meaning:

• since childhood
• since she was a girl

Adding an article would change the meaning and sound unnatural in this context.

Because Spanish often leaves out the article when talking about things in a general sense, especially after certain verbs.

So:

• lee novelas = she reads novels
• come verduras = she eats vegetables
• compra libros = she buys books

If you said lee las novelas, it would usually sound more specific, like she reads the novels—particular novels already known in the conversation.

Here, una editorial means a publishing house / a publisher.

This is an important false friend for English speakers, because editorial in English usually means a newspaper opinion piece. In Spanish, editorial can mean that too in some contexts, but after trabaja en una, it clearly means publishing company.

So:

• trabaja en una editorial = she works at a publishing house

Because trabajar en is commonly used to mean to work in/at a place or company.

• trabaja en una editorial = she works at a publishing house

You can also hear trabajar para when the idea is to work for someone or some organization:

• trabaja para una editorial = she works for a publishing house

Both can be possible, but en focuses more naturally on the workplace/company as the place of employment.

Ahora means now or nowadays / currently.

It helps connect the two ideas:

• she has read novels since childhood
• and now she works in publishing

So it highlights a present situation that fits nicely with the first part of the sentence. It can suggest a kind of life development: she loved reading as a child, and now she works in that world professionally.

Because Spanish often omits subject pronouns when the verb ending already makes the subject clear.

In this sentence:

• lee already tells us the subject is she/he
• trabaja also tells us the subject is she/he

Since mi amiga has already been mentioned, repeating ella is unnecessary.

So Spanish naturally says:

• Mi amiga lee novelas desde niña y ahora trabaja en una editorial.

Instead of:

• Mi amiga lee novelas desde niña y ella ahora trabaja en una editorial.

The second version is possible, but less natural unless you want extra emphasis.

Literally, niña means girl. But in this sentence, a very natural English translation is often since she was a child.

That is because English usually prefers child in this kind of general time expression, even though Spanish uses the feminine niña to match the female subject.

So depending on style, you could understand it as:

• since she was a girl
• since she was a child
• since childhood

All of these work well in context.

Yes. Both main verbs are in the present tense:

• lee = reads / is reading
• trabaja = works / is working

But the first present tense has an ongoing-from-the-past meaning because of desde niña. That is why English often translates it with a present perfect idea:

• She has been reading novels since childhood, and now she works at a publishing house.

So grammatically it is present tense in Spanish, even if English may translate part of it differently.